The invention relates to a tilting device for a marine drive unit, such as an outboard engine or the outboard drive portion of an inboard/outboard engine for boats, rafts and other marine vessels which prevents the drive unit, when in the tilted-down position, from freely moving toward the tilted-up position during normal operation.
One form of outboard drive unit is attached to the hull of a marine vessel by a clamp bracket and an elongated swivel bracket secured to the clamp bracket by a tilt shaft that allows the drive unit to be selectively tilted downwardly into, or upwardly out of, the water. This type of swivel bracket is normally used on vessels having a high transom such as sail boats.
A lower position stop pin, engageable with the swivel bracket, is typically used for setting downward position of the swivel bracket.
In order to perform satisfactorily, the drive unit should preferably include a tilt cylinder device, having two check valves and a bypass valve. With such a device, the swivel bracket, when maintained in the tilted-up position, can be rotated to its tilted-down position against the pressure of an assist gas because the second check valve permits the release of pressure even when the bypass valve is closed.
When the bypass valve is in the open position and the swivel bracket is in the tilted-down position, however, the swivel bracket is moveable toward the tilted-up position when the vessel is driven in the reverse direction. The tilting device is arranged to automatically prevent such free movement. The tilting device is arranged so that the bypass valve of the tilt cylinder device is automatically closed when the swivel bracket is rotated to the tilted-up position. The tilting device is further arranged so that the bypass valve remains in the closed position when the swivel bracket is tilted down, thereby preventing the drive unit from freely tilting up during normal operation.